The present invention relates to wound dressings, and pertains more particularly to wound dressings primarily for application over wounds which would be expected to exude substantial amounts of fluid during the normal healing process.
Exudation from many types of skin lesions is normal during the healing process. Included are such wounds as Stage II and Stage III ulcers, second and third degree burns, skin grafts and donor sites, deep derm abrasions and lacerations. Conventional bandages or wound dressings readily absorbed fluids, when used for such lesions, and soon become saturated with exudate seeping from the open wound, necessitating frequent bandage or dressing changes. The frequent changes cause irritation of the wound, discomfort to the patient and increased health care costs. A wound dressing which would have the capability of absorbing exudate as it appears at the surface of an open wound and the ability to transmit absorbed moisture at a desired rate through the dressing to the backing layer (sometimes herein referred to as the "distal surface" of the dressing, the surface furthest removed from the wound when the dressing is in place over the wound) where it can evaporate from the dressing would be particularly useful as a wound covering. Since such dressing could remain in place over the wound without needing to be changed for a longer period of time than conventional dressings, the wound would not be disturbed as frequently as a result of dressing changes and the patient would not experience as much discomfort from the associated trauma.
Various attempts have been made to provide a wound dressing that is capable of more effectively absorbing exudate seeping from an open wound.
In U.S. Pat. No. 3,339,546, a dressing comprised of a water-impervious film having an adhesive layer plied with the water-impervious film is described. The adhesive layer is disclosed as being a blend of a water-soluble or water-swellable hydrocolloid material dispersed throughout a water-insoluble viscous elastic binder.
U.S. Pat. No. 3,972,328 describes a wound dressing consisting of three components, namely, (1) a middle layer comprised of a semi-open cell flexible foam, (2) a water-impervious flexible film attached over one surface of the middle layer, and (3) a pressure-sensitive adhesive layer disposed over the other surface of the middle layer. The pressure-sensitive adhesive component is formed of a pressure-sensitive elastomer containing a water-soluble or water-swellable hydrocolloid or mixture of such hydrocolloids and contains, additionally, a tackifier and a plasticizer or solvent.
Although the use of water-soluble or water-swellable hydrocolloids dispersed in the adhesive layer of a wound dressing allows wound exudate to be absorbed by the hydrocolloids, the absorption of the exudate by the particles of hydrophilic material, with attendant swelling of the particles, prematurely destroys the integrity of the adhesive film resulting in the film's disintegration.